Smoothing is a general operation that can be applied on a three-dimensional geometrical primitive, such as a mesh or NURBS surface, to reduce high-frequency variations of geometric properties, such as positions and colors. In the context of two-dimensional or three-dimensional geometric primitives, smoothing is usually performed by applying a local averaging filter over each vertex and their neighbors. The definition of neighbors may be based on connectivity, spatial proximity or other characteristic. Such smoothing can be applied to achieve animation effects.
For three-dimensional objects, smoothing can be applied on control vertices of a shape in order to enhance it relatively to one of the many esthetic criteria. Such criteria may include low-frequency curvature, locally equilateral segments, and locally equiangular connectivity around a vertex local grid alignment.
Without fine control, smooth operations produce an overwhelming number of mixed effects. Depending on the artistic context, some of these may cause undesirable behaviors, such as failing to preserve either the shape or other properties such as local convexities and concavities.